Many supercomputing applications employ super conducting circuits that are predominantly implemented in integrated circuits. These integrated circuits often perform best when operating in a cryogenic environment that is maintained at or near cryogenic temperatures, which may extend down to or below 4 (four) Kelvin (K).
In a cryogenic environment, the circuit boards on which the integrated circuits reside generally operate in a medium to high vacuum to avoid convective heat leakage and various gasses condensing on the surface of the circuit boards and the integrated circuits residing thereon. This leaves conduction as the main method of removing heat from the integrated circuits. The heat generated from the integrated circuits can be transmitted through the solder connections (i.e. a ball grid array) to a circuit board and then to a heat sink, which is made of aluminum, copper, or like material that is highly thermally conductive.
Unfortunately, the materials used for the integrated circuits, the circuit boards, and the heatsinks are different and have widely varying coefficients of thermal expansion (CTEs). The thermal contraction and expansion associated with cycling the system between 293 K to 0 K are extreme and vary from material to material. As a result, the integrated circuits may be damaged and/or break loose from the circuit boards to which they are attached. The expansion and contraction of the heatsinks at different rates than the circuit board may fracture the circuit boards under compressive and/or tensile stresses as well as break the thermal bond between the circuit boards and heat sinks. Any damage to the integrated circuits, circuit boards, or electrical connections therebetween leads to failure of the overall system. Further, a failure in the thermal bond between the circuit board and the heat sink may lead to overheating and failure of the integrated circuits and/or the circuit boards.